Technical Field
The technology relates to structures and methods for forming high doping concentrations by implantation in ultrathin layers of semiconductor-on-insulator substrates.
Discussion of the Related Art
Transistors are fundamental device elements of modern digital processors and memory devices, and have found numerous applications in various areas of electronics, including power electronics. Currently, there are a variety of transistor designs or types that may be used for different applications. Various transistor types include, for example, bipolar junction transistors (BJT), junction field-effect transistors (JFET), metal-oxide-semiconductor field-effect transistors (MOSFET), vertical channel or trench field-effect transistors, and superjunction or multi-drain transistors. One type of transistor that has emerged within the MOSFET family of transistors is a fin field-effect transistor (finFET). The finFET is a three-dimensional structure for which a channel, source, and drain are formed on a narrow fin protruding from a substrate.
In some cases, dopants may be introduced into a transistor structure or into nearby structures to induce strain in a channel region of the device, or to improve electrical characteristics of the device. For example, germanium (Ge) may be added to a transistor formed in silicon (Si) to convert the channel region to SiGe or to strain the transistor's channel. SiGe can exhibit higher carrier mobility than Si semiconductors. Straining of a channel can improve carrier mobility in the channel for both n- and p-type devices.